Abstract
Mass vaccination campaigns with the oral poliovirus vaccine targeting children aged <5 years are a critical component of the global poliomyelitis eradication effort. Monitoring the coverage of these campaigns is essential to allow corrective action, but current approaches are limited by their cross-sectional nature, nonrandom sampling, reporting biases, and accessibility issues. We describe a new Bayesian framework using data augmentation and Markov chain Monte Carlo methods to estimate variation in vaccination coverage from children's vaccination histories investigated during surveillance for acute flaccid paralysis. We tested the method using simulated data with at least 200 cases and were able to detect undervaccinated groups if they exceeded 10% of all children and temporal changes in coverage of ±10% with greater than 90% sensitivity. Application of the method to data from Pakistan for 2010–2011 identified undervaccinated groups within the Balochistan/Federally Administered Tribal Areas and Khyber Pakhtunkhwa regions, as well as temporal changes in coverage. The sizes of these groups are consistent with the multiple challenges faced by the program in these regions as a result of conflict and insecurity. Application of this new method to routinely collected data can be a useful tool for identifying poorly performing areas and assisting in eradication efforts.
Highlights
We have described a new method for estimating vaccination campaign coverage from routinely collected acute flaccid paralysis (AFP) data that allows the identification of persistently undervaccinated children as well as temporal changes in coverage while accounting for errors in reporting
While current assessments of supplementary immunization activity (SIA) performance are informative, they mask some of the heterogeneity present in the data and represent an average across children of different ages who have been exposed to different SIAs
It is clear from the crude analyses and our new model that Balochistan/Federally Administered Tribal Areas (FATA) has suboptimal coverage and a persistently undervaccinated group of children, but the heterogeneity in coverage within Khyber Pakhtunkhwa (KP) was not apparent using the crude analyses, since the proportion of children with more than 3 doses was high and the proportion of zero-dose children was low
Summary
The estimates of coverage from the heterogeneous-temporal model fitted the simulated data well and maintained a high sensitivity and specificity for detecting undervaccinated groups. We have described a new method for estimating vaccination campaign coverage from routinely collected AFP data that allows the identification of persistently undervaccinated children as well as temporal changes in coverage while accounting for errors in reporting.
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